In recent developments of telecommunications technology and, in particular, in the development of broadband integrated services networks (B-ISDN), the asynchronous transfer mode (ATM) based on asynchronous time-division multiplex technique plays a significant part. The signal transmission is consequently undertaken in a bit stream that is subdivided into cells, each respectively composed of header and useful information part, of a constant length of, for example, 53 octets that are occupied as needed with packeted messages. Special empty cells are transmitted when no useful information is to be currently communicated. Virtual connections, i.e. connections that only in fact use a path section when a message packet (block) is in fact to be communicated via the path section are set up in ATM switching centers, whereby every packet contains, among other things, an address covering, for example, two octets in its header for the unambiguous allocation of the packet to a specific virtual connection. Based on the measure of the respective selection information, every packet at the input to the switching network can thereby contain the complete information for its route through the switching network. Using this information, the switching elements themselves then switch the packet on the defined route (self-routing network) (see, for example, Telcom Report 11 (1988) 6, 210 . . . 213). A two-stage reversing switching network having (32.times.32) switching matrices can thereby be provided as the switching network, these switching matrices being in turn each respectively capable of being formed of four switching pyramids formed with (16.times.8) switching elements (see, for example, ISS'90 Proceedings Vol. 1, Paper A2.3, FIG. 10). Since switching equipment must guarantee a practically interruption-free switching operation, at least two redundant switching levels will be provided, i.e. the switching network will be doubled (see, for example, EP-A1-0 384 936).
When establishing switching centers, the case is often is such that, given what is initially a limited number of subscribers, a fully expanded switching network is not initially required. On the contrary, only a partially expanded switching network is adequate, which is capable of being later expanded to form a fully expanded switching network. In order to be able to undertake such an expansion without interrupting operations, a maximally configured, second (reversing) switching stage is usually provided from the very outset in a two-stage reversing switching network even when this only has a partial configuration level. The switching matrices of the second (reversing) switching stage that are already provided in a partial configuration of the switching network, but that are not yet required, then represent an unutilized dedicate resource.